Insulation of finely-divided magnetic material



Dec. 6, 1927. 1,651,958

H. H. LOWRY INSULATION OF FINBLY DIVIDED MAGNETIC MATERIAL Filed Jan.5, 1927 by i. 55W

Affamey 600 C. and the rings are thereafter cooled. sulatin g properties at the temperatures of During this heat treatment the zinc-oxide which is used as a flux for the magnesium oxide is partially dissociated and volatilized, the oxygen resulting from the dissociation combining with the magnetic particles to form a combination of nickel and iron oxide on the surfaces of the particles which further increases the insulation. The-high temperatures of the heat treatment do not a'p-' preciably affect the insulating properties of the magnesium oxide coating, this being stable within the range of the heat treating temperatures. For a detailed account of heat treatments employed with nickel iron alloys, reference is made to patents to G. W.

Elmen Nos. 1,586,884 and 1,586,889.

When a core is to be made, in accordance with this invention, for a telephone loading coil, a plurality of these rings are stacked coaxially to form a complete core, as shown in Fig. 2, on which the usual toroidal wind-' ing is applied, the number of rings used de pending upon the existing electrical characteristics of the telephone circuit with which the loading coils are to be associated.

While the invention has been described with respect to the insulation of magnetic dust which is subject to a heat treatment to improve the magnetic properties of the magnetic material, the invention is not limited tothis particular aspect. The magnesium oxide-zinc oxide insulation may be employed in other forms of metallic structures which are subject to heat treatment after the insulation has been applied. Furthermore, the

specific proportions of the oxides may be varied, depending on the properties of the memagnesium oxide and zinc oxide.

3. A magnetic structure comprising an alloy' including nickel-iron in finely divided form, said alloy requiring heat treatment at a high temperature to improve the magnetic properties-of the core, and an adherent insulating coating on the particles consisting of magnesium oxide, zinc oxide and oxides of IllOkBl flIld lIOIl, sa1d coatlng retammg its inthe heattreatment.

4. A magnetic structure comprising an alloy containing nickel and iron in finely divided form, the particles being capable of passing through a sieve having 120 meshes per inch, and an adherent insulating coating on the particles comprising magnesium oxide and zinc oxide, the volume of theoxides being approximately 6% of the volume of the magnetic particlesand the volumes of the two oxides being substantially equal.

5. The method of producing magnetic structures, which comprises coating magnetic particles with'a composition containmg magnesium hydroxide and zinc hydroxide and heating the coated particles to change the hydroxides to oxides.

6. The method of producing magnetic structures, which comprises coating mag-.

netic particles with a mixture of magnesium hydroxide and zinc hydroxide, heating said particles to change the hydroxides to adherent oxides, and subjecting the oxide coated particles to high pressures to form a homogeneous solid.

7. The method of producing magnetic structures, which comprises coating particles of an alloy comprising nickel-iron with a mixture of magnesium hydroxide and zinc hydroxide, heating sai'd particles to convert the hydroxides to oxides, and subjecting a mass of oxide-coated particles to high pressure to combine the coated particles into a homogeneous solid.

8. The method of insulating nickel-iron alloy in a finely 'divided state, which comprises mixin a mass of alloy particles with magnesium. ydroxide and zinc h droxide, the total volume of the hydroxide eing approximately 6% of the volume of the alloy mass, to form a coating on the particles, and heating the mixture to change the hydroxides to oxides.

9. The method of producing a magnetic core, which comprises coating particles of an alloy comprising nickel and iron with a mixture of magnesium hydroxide and zinc hydroxide, heating said coated particles to form an adherent coating thereon of magnesium oxide and zinc oxlde, forming a mass of sa1d particles into a homogeneous solid under high pressure, and heat treating said solid to improve the magnetic properties of said nickel-iron alloy.

In witness whereof, I'hereunto subscribe my name this 30th day of December, A. D.,

,HOMER H. LownY. 

